Ground speed indicator



Sept. 27, 1927.

R. KAUCH ET AL GROUND SPEED INDICATOR 1N VENTOR Rainer! fiauch Filed July 1'7, I 1924 B y 6h arleaL. Pau/ua M A 7 RNE Patented Sept. 27, 1927.

UNITED STATES ROBERT KAUdH AND CHARLES L. PAULUS, F DAYTON, OHIO.

GROUND SPEED INDICATOR.

- Application filed July 17, 1924. Serial No. 726,551.

This invention relates to ground speed inlicators for aircraft.

The principal object of the invention 15 to provide a ground speed indicator capable of giving direct readings which is self-contained in that its operation does not rely on any settings determined fromreadlng of other instruments such as altimeters or the like, with a view to securing an instrul0 ment of greater accuracy.

With the foregoing object in mind, the invention provides an instrument comprlsing a sight for sighting on a vertical line 'to the ground the obpects are not distinguished, but the ground appears as a blur as it sweeps past, and a driven member such as a slotted disc for producing another blur similar to the ound blur super-imposed on the ground blur, the driven member being operated at varying speeds until the blurs are in synchronism, at which time the speed of the driven member is determined and expressed in terms of ground speed.

Other objects having reference to details of construction in an instrument embodying the invention are brought out with the foregoin object in the course of the following detai ed description, in which reference is 3 made to the accompanying drawing illustrating the invention:

Fig. 1 is a plan view of an instrument made in accordance with our invention.

Fig. 2 is a front elevation of Fig. 1.

Fig. 3 is an enlarged fragmentary detail partly in section of the sight and the driven member forming the principal parts of the instrument.

The instrument is desi ed to be sighted by the pilot or observer t rough an opening in the fioor of the cockpit, and comprises'a bracket 10 supporting a sight 11 held in a vertical position to sight on a vertical line to the ground. An eye piece 12 is preferably provided on the upper end of the sight 11 which, it will be noted, is tubular in form and tapered at the lower end to have an elongated sight opening 13. The opening 13 extends approximately at right angles to slots 14 extending radially from the periphery of a disc 15 mounted on a vertical spindle 16 supported in a bearing 17 on the bracket 10. The disc 15 has its slotted por-.

tion operating beneath the sight 11 to interrupt the view of the ground with a blur produced by the periodic appearance of the in a restricted manner so that regularly spaced slots 14. The ground as at too great a speed, a blur will be, observed which apparently moves to the rear. The blur seen is actually the result of compounding the blur of the disc on the ound blur. When the disc is rotated at too s ow a speed, the resulting blur apparently moves forward. When, however, the proper speed is given the disc, the blur of the disc is in synchronism with the ground blur and, as a result, the blur seen stands still or quivers slightly. The disc 15 as will be described presently, has means associated therewith for driving the same at varying speeds and .it is at the time that the disc is driven so that a stationary blur is produced that the speed of the disc is noted to determine the ground speed.

The purpose for providing an elongated sight opening was partly to confine the vision to a certain point ,on the disc and thus avoid confusion in determining the exact point at which the blurs blend. Also, due to the fact that the slots move in a circle, confusion would'result by the slots assumingdifferent angularity relative tothe opening or entering into view and leaving. By narrowing1 the opening, the slots appear to move as t gation of theslot was found necessary due to the fact that the human vision is limited as to the quickness with which it picks up objects or adjusts its focus; thus, in the present case, it is necessary for the eye to get a glimpse of the ground as the slot in the disc appears. With the slot 13 of the proper length, it is found possible to compare the blur of the ground with the blur of the disc without any noticeable eye fatigue. j

The disc 15 is driven suitably by hand by a belt 18 passing about a pulley on the spindle 16 and about another pulley on a shaft 19 driven by a bevel gear 20 which in turn meshes with a hand driven bevel gear 21. The latter has a handle 22 on the face thereof within convenient reach of the pilot or observer. The shaft 16 is fitted at its upper end with a tachometer 23 having ough on a belt, orthe like. Elona scale 24 calibrated in terms of ground speed.

The operation is as follows. The pilot, observing through the sight 11, drives the disc 15 by turning the gear 21 by hand. The apparent movement of the blur produced by the super-imposing of the disc blur on the ground blur is an indication as to whether the disc is being driven too fast or too slow. On properly varying the speed, a practically stationary blur or a slightly quivering blur is obtained. The pilot then secures the ground speed by observing the reading of the tachometer. It is apparent that greater accuracy is obtainable with an instrument of this kind where it is not necessary to depend on a setting determined by the reading of another instrument. In previous types of ground speed indicators, altimeter readings were usually used in determining ground speed, and this compounded an error resulting from the inaccuracy of the altimeter on the inherent inaccuracy of the ground speed indicator. The present instrument has been found to give round speed valueswith accuracy to withln three and four percent. Such an error or even greater errors are ordinarily involved alone in the altimeter readings.

We claim 1. In a ground speed indicator, a sight for causing the ground to appear as a blur, a member driven at a fast rate of speed having openings therein through which intermittent glimpses of the ground blur are seen through said sight, the openings in said mem ber causing it in moving to appear as a blur, means for varying the speed of said driven member to bring said blurs to synchronism and means to measure the speed of said driven member.

2. In a ground speed indicator, a sight for causing the ground to appear as a blur, a member driven at a fast rate of speed having openings therein through which intermittent glimpses of the ground blur are seen through said sight, the openings in said member causing it in moving to appear as a blur, means for varying the speed of said driven member to bring said blurs into synchronism, and means to measure the speed of said driven member, directly in terms of ground speed.

3. In a round speed indicator, a sight for viewing t e ground so it appears as a blur, drivable means associated with said sight, said means to be driven at varying speeds to produce another blur super-imposed on said first blur, and means to determine the speed of said last mentioned means, when said blurs blend.

4. In a ground s eed indicator, a sight for viewing the groun so it appears as a blur, drivable means adjacent the end of said sight, means to be driven at varyingspeeds to :ueaaaer produce another blur super-imposed on said first blur, and means to determine the speed of said last mentioned means.

5. In a ground speed indicator, a vertically fixed sighting member having an elongated sight opening, drivable means disposed beneath said opening, said driven member having openings therein through which intermittent glimpses of the ground are seen through said sight opening.

6. In a ground speed indicator, a fixed sighting member having an elongated sight opening, drivable means disposed beneath said opening, said member having openings therein through which intermittent glimpses of the ground are seen as a blur through said driven sight opening, means to operate said driven member at varying speeds to produce a blending of the ground blur with the blur produced by said member,in moving, and means to measure the speed of said member.

7. In a ground speed indicator, a sight for keeping a vertical line of sight to the ground, and viewing the same restrictedly so it appears as a blur, a driven member disposed beneath said sight for producing a blur visible in said sight, the blur of the ground sweeping by bein visible behind the blur produced by said driven member,-means for driving said member at varying speeds to secure synchronism between the blurs, the

said blurs then appearing approximately stationary, and means to indicate the ground speed when said blurs come into synchronism.

8. In a ground speed indicator, a sight for keeping a vertical line of sight to the ground, and viewing the same restrictedly so it appears as a blur, a driven member disposed beneath said sight and adjacent thereto for producing a blur visible in said sight, manually operable means for driving said member at varying speeds to secure synchronism between blurs, and means to indicate the ground speed when said blurs come into synchronism. A

9. In a ground speed indicator, a fixed vertically mounted ground sight, a slotted openin in said sight and a driven disc having a fiotted portion to be viewed through said slotted opening in said sight interrupting the sighting to the ground.

10. In a ground speed indicator, a fixed vertically mounted ground sight, a driven disc having a portion provided with openings through which intermittent glimpses of the ground are seen, means to drive said disc at varying speeds, and a tachometer for measuring the speed ofvsaid disc.

11. In a ground speed indicator, a vertically mounted ground sight, a driven disc moving within the line of vision of said ground sight having a portion provided with openings through which intermittent glimpses of the ground are seen, means to drive said disc at varying speeds, and a tachometer on the same, fixed with said disc for measuring the speed thereof directly in terms of ground speed.

12. In a ground speed indicator, a revolving member having radial slots therein, and a vertically fixed sight having an elongated sight opening transverse to said radial slots as they sweep by the sight opening.

13. In a ground speed indicator, a support, a bearing thereon,-'a vertical spindle in said bearing, a slotted disc on the lower end of said spindle, a tachometer device connected to the upper end of said spindle, manually operated driving means for rotating said-spindle, and a vertically mounted sight for viewing downwardly through the slotted portion of said disc.

14. In a round speed indicator, a support, a bearing thereon, a spindle mounted in said bearing, a rotating member fixed on one end of said spindle having openings therein, means connectedto the other end of said spindle to indicate the speed thereof directly in terms of ground speed, driving means for said spindle, and a sight mounted adjacent said rotating member for viewing through the openings therein.

15. In a ground speed indicator, fixed means for keeping a constant intermittent line of sight to the ground, a driven part, the speed of which may be determined in terms of ground speed, said part being visible through said sighting means to compare the sweep thereof with the sweep of the ground, and means indicating difierent ground speeds for different speeds of said driven part. 7

16. In a ground speed indicator, fixed means for keeping a constant intermittent line of sight to the ground with restricted vision, a driven part, the speed of which may be varied until the sweep thereof past said sighting means is approximately the same as the apparent sweep of the grounu past said sighting means, and means for in dicating different ground speeds for diifer' ent speeds of said driven parts.

17.'In a ground speed indicator, means for keeping a constant intermittent line of sight vertically to'the ground, a driven part adjacent thereto the speed of which may be varied until the sweep thereof past said sighting means is approximately the same as the apparent sweep of. the ground past the said sighting means, and means indicating different ground speeds for different speeds of said driven part.

18. The method of determinin the ground speed of aircraft which consists in sighting the ground so that it appears to pass in'the form of a blur, driving a drivable part to cause a second blur to be superimposed on the first mentioned blur, vary ing the speed of the drivable part to cause said blur to appear approximately stationary, and then measuring the s eed ofthe driven part in terms of groun speed.

19. In a grgund spieed indicator for aircraft, a member for eeping a vertical line of sight to the ground, and viewing the same so restricted so it appears as a blur, a driven member vadjacent said first member for producing a blur visible in said sight, manually operable means for varying one of said members to vary the appearance of one of said blurs, to secure similarity in the a pearance of said blurs, and means to in cate the ground speed when said blurs appear similar.

In testimony whereof we aflix our signatures.

ROBERT KAUGH. CHARLES L. PAULUS. 

